The present invention relates to radio-electronic technology and, more specifically, to processes for producing non-porous coatings on corundum substrates.
The present invention is useful for the production of integral circuits and other micro-circuits as well as precision resistors.
Recently there have been developed low-porous (porosity up to 1-3%) ceramic substrates; nevertheless, the progress in miniaturization of micro-circuits imposes more stringent requirements upon the surface quality of such substrates. Ceramic corundum substrates now in use in electronics for some types of integral and other micro-circuits can withstand, unlike glass and ceramic glass, temporary action of high temperatures above 1,000.degree. C and have better mechanical, electrical characteristics and greater thermal conductivity.
One approach to the improvement of the surface quality of ceramic substrates resides now in glazing thereof, i.e. applying glaze on the surface of ceramic corundum substrates with the corundum content of 90 to 100%, followed by heat-treating thereof.
This prior-art process of glazing is, however, applicable only for corundum substrates having surface roughness corresponding to the surface finish of class 10 and does not prevent such a defect as undulation, while a thickness of a well-formed glaze layer is at least 20 to 60 mom. A glaze layer of such thickness impairs electrical properties and lowers thermal conductivity of substrates.
Furthermore, a disadvantage of said prior-art process that the operating temperature of glazed substrates does not exceed 700.degree. or 800.degree. C.